PHENYLKETONURIA: A METABOLIC DISORDER

Metabolic disorders are genetic diseases that affect the body's ability to perform its normal chemical reactions. Many metabolic disorders result from enzyme defects. Recall that a metabolic pathway is a stepwise sequence of enzyme-mediated reactions. If one enzyme in a metabolic pathway is defective, that enzyme's substrate may accumulate and the pathway may not be completed. This may result in a buildup of harmful substances or a shortage of required molecules.

ACTIVITY

In this exercise, you will use the Web links below to gather information about the metabolic disorder phenylketonuria (PKU). Use what you learn to answer the questions at the bottom of the page.

Your Genes, Your Health: Phenylketonuria
http://vector.cshl.org/ygyh/mason/ygyh.html?syndrome=pku

NSPKU Home Page
http://web.ukonline.co.uk/nspku/

Texas Department of Health Genetic Disorders
http://www.tdh.state.tx.us/newborn/what_pku.htm

Phenylketonuria - The Genetics
http://willroberts.com/pku/

Questions

1. What enzyme is most commonly defective in people with phenylketonuria?
2. What reaction does this enzyme catalyze? (What is the substrate and what product is produced?)
3. Describe the symptoms of phenylketonuria.
4. What causes the symptoms of PKU, the lack of a substance or the buildup of one?
5. How common is phenylketonuria? How is it treated?